Review of Greenland activities 1997 - Geus

More documents

Recommendations

Info

Fig. 6. View of the 300 m high part of Hareøen showing an E–W trending fault displacing the lower part of the Vaigat Formation. correlation between onshore structural data and offshore seismic data are necessary in order to establish a structural model for the development of the Nuussuaq Basin. The stereo-photography programme referred to above was extended to areas around Sikillingi, Marraat, Bartschiakløft, Kuugannguaq and Hareøen (Fig. 6). Studies of hydrothermal alteration A new research programme was initiated in 1997 to assess the nature of hydrothermal alteration within the Tertiary lavas of Disko, Nuussuaq, and Hareøen. The main aims of this work are: (1) identification and mapping of regionally extensive depth-controlled secondary mineral isograds throughout the province; and (2) documentation, sampling, and mapping of hydrothermal veins and replacement alteration in the Marraat area. These objectives were met through regional-scale mapping and outcrop-scale observations and sampling. Investigations of regional alteration patterns concentrated on identification of regionally extensive zones characterised by secondary mineral assemblages dominated by zeolites. Similar sets of zeolite zones have been observed in other parts of the North Atlantic Tertiary igneous province (e.g. Walker 1960a, b; Jørgensen 1984; Neuhoff et al. 1997) where they are sensitive indicators of the thermal (Kristmannsdóttir & Tómasson 1978) and lithological structure (e.g. Walker 1960a) of the upper crust. The zeolite zones indicate the palaeothickness of the now partly eroded Tertiary flood basalts in the province, and make it possible to interpret the geothermal gradient in the lava series shortly after the eruption of the basalts. Systematic mapping of zeolite zones along the south-western, southern, eastern and northeastern coasts of Disko, south-western Nuussuaq and Hareøen indicates that most of the exposed lavas have undergone regional low-grade metamorphism (< 100ºC based on the presence of the chabazite-thomsonite, analcime, and mesolite-scolecite zones) in response to geothermal gradients ≤ 30ºC/km. Reconnaissance mapping along the southern coast of Nuussuaq west of the Itilli fault zone suggests that these lavas were altered at significantly higher temperatures (≥ 100ºC based on exposures of laumontite and stilbite-heulandite bearing lavas) and tilted westward after regional metamorphism. Assuming that the geothermal gradient is ≤ 30°C/km, then the zeolite zones present in the area indicate an erosion factor less than expected. Detailed outcrop and kilometre-scale investigations were conducted in order to determine the conditions, relative timing, structural environment, and relationship to oil migration of various stages of alteration present in the Marraat region. Early regional alteration (dominated by thomsonite with local development of chabazite and analcime) fills primary pore spaces in the lavas and is overprinted by several prominent vein sets. The most prominent of these veins in outcrop are filled with silicate-bearing (xonotlite, pectolite, or natrolite) mineral assemblages and occur together in infrequent swarms as reported by Karup-Møller (1969). Other less prominent but more common veins filled with quartz or calcite or both frequently post-date the silicate veins. Certain carbonate veins contain petroleum and appear 15
to be conduits for migration; lavas hosting these veins are petroliferous and exhibit extreme CO 2 metasomatism that replaced (often pseudomorphically) earlier Ca-silicate alteration with silica-clay-carbonate assemblages. Preliminary field results and planned analysis of samples collected in 1997 will provide fundamental data for assessing the physical and chemical nature of petroleum systems in West Greenland. Regional alteration patterns (i.e. zeolite zones) constrain the pre-erosional thickness of the lava pile, thermal gradients during regional alteration, and the timing and orientation of structural deformation within the lava pile (cf. Neuhoff et al. 1997) necessary for evaluating the burial and thermal history of the underlying sedimentary basin(s). Determination of vein mineralogy, orientation, frequency and timing promises to provide at least semi-quantitative constraints on the magnitude, direction and composition of groundwater migrating through the reservoirs. Lastly, the apparent spatial and causal relationships between petroleum-bearing veins and carbonate-metasomatism may offer a new exploration tool for identifying petroleum migration paths in basaltic reservoirs. Commerical exploration by grønArctic Energy Inc. Compared to the very active year of 1996 when grønArctic carried out a major airborne geophysical survey and drilled a c. 3 km deep exploration well, GRO#3, on Nuussuaq (see Christiansen et al. 1997), the level of commercial exploration activity was very low in 1997 and did not include any field work, geophysical surveys or drilling. In 1997 grønArctic gave up their license that covered 1011 km 2 on eastern Disko, together with a few valleys in central and northern Disko. By the end of 1997 grønArctic had relinquished further areas on Nuussuaq so the company’s remaining licence area is reduced to 390 km 2 . Future work Field work, analytical studies and regional interpretation of the development of the Nuussuaq Basin will continue in the coming years, and will include a variety of geological disciplines. Results from the sedimentological, structural, volcanic and zeolite minerals studies will add considerable knowledge to the understanding of the petroleum system of the Nuussuaq Basin, especially with respect to source and reservoir rocks and timing of trap formation and maturation. Considerable analytical effort will be used to study the distribution and origin of the different oil types, and their implications for the exploration potential of the Nuussuaq Basin as well as for the neighbouring offshore basins. Additional field work may add new localities to the encouraging pattern that has been demonstrated so far. Infill sampling is necessary in some areas whereas areas without previous evidence of oil shows (e.g. on western Disko) will be checked. The presence of sediment-contaminated volcanic rocks with magma-modified carbon and sulphide-rich sedimentary xenoliths along the entire west coast of Disko indicates the existence of marine carbonaceous sediments beneath the basalts west of the Disko gneiss ridge over very large areas. This makes western and south-western Disko a natural target for systematic ‘oil hunting’ in the future. Acknowledgements Funding of the field work and the subsequent analytical work was provided by the Government of Greenland, Minerals Office (now Bureau of Minerals and Petroleum). Mobilisation of the field camps took place from Arktisk Station, Godhavn with the help of the ship Maja S. Finn Steffens and his crew, Peter Broberg, Peter Brandt and Martin Broberg, are thanked for good seamanship, hard work and much practical help. References Bojesen-Koefoed, J.A., Christiansen, F.G., Nytoft, H.P. & Pedersen, A.K. in press: Oil seepage onshore West Greenland: evidence for multiple source rocks and oil mixing. In: Fleet, A.S. & Boldy, S. (eds.): Petroleum geology of Northwest Europe. Proceedings of the 5th conference. London: Geological Society. Christiansen, F.G., Bojesen-Koefoed, J., Nytoft, H.-P. & Laier, T. 1996: Organic geochemistry of sediments, oils and gases in the GANE#1, GANT#1 and GANK#1 wells, Nuussuaq, West Greenland. Danmarks og Grønlands Geologiske Undersøgelse Rapport 1996/23, 35 pp. Christiansen, F.G., Boesen, A., Dalhoff, F., Pedersen, A.K., Pedersen, G.K., Riisager, P. & Zinck-Jørgensen, K. 1997: Petroleum geological activities onshore West Greenland in 1996, and drilling of a deep exploration well. Geology of Greenland Survey Bulletin 176, 17–23. Dam, G. & Sønderholm, M. 1998: Sedimentological evolution of a fault-controlled Early Paleocene incised-valley system, Nuussuaq Basin, West Greenland. In: Shanley, K.W. & McCabe, P.J. (eds): Relative role of eustacy, climate, and tectonism in continental rocks. SEPM Special Publication 59, 109–121. Tulsa, Oklahoma: Society for Sedimentary Geology. 16
Page 1 and 2: GEOLOGY OF GREENLAND SURVEY BULLETI
Page 3: Geology of Greenland Survey Bulleti
Page 6 and 7: Contents Bold numbers refer to the
Page 8 and 9: A review of Greenland activities, 1
Page 10 and 11: using Greenland-trained prospectors
Page 12 and 13: Canada Svartenhuk Halvø M Karrat I
Page 14 and 15: Fig. 3. Mid-Cretaceous sandstones o
Page 18 and 19: Dam, G., Larsen, M. & Sønderholm,
Page 20 and 21: Svartenhuk Halvø Greenland Ubekend
Page 22 and 23: 1974) and in 1978 by M.V. Dana (Bre
Page 24 and 25: offshore Marraat Killiit, where the
Page 26 and 27: these areas must therefore be treat
Page 28 and 29: Olsen, T. & Pedersen, G.K. 1991: Th
Page 30 and 31: SW 0 km 10 km 20 km 30 km 40 km 50
Page 32 and 33: Diagenesis and reservoir properties
Page 34 and 35: Fig. 3. Paragenetic sequence of dia
Page 36 and 37: Petroleum geological activities in
Page 38 and 39: Fig. 2. Incised valley in the proxi
Page 40 and 41: The thickest and most complete Jura
Page 42 and 43: 250 PALAEOZOIC 200 150 MESOZOIC 100
Page 44 and 45: Sequence stratigraphy of source and
Page 46 and 47: W PLATFORM BASIN E HST SB 2 SB 3 HS
Page 48 and 49: TRIASSIC JURASSIC RHAETIAN HETTANGI
Page 50 and 51: Cretaceous STAGES Volgian South 120
Page 52 and 53: Member, has a very low content of m
Page 54 and 55: Upper Permian Ravnefjeld Formation
Page 56 and 57: Wandel Sea Basin, eastern North Gre
Page 58 and 59: Greenland, and along the zone of la
Page 60 and 61: Fig. 3. Unconformity between faulte
Page 62 and 63: Tertiary to Recent uplift is propos
Page 64 and 65: Airborne geophysical surveys in cen
Page 66 and 67:
lock is located in northern Jameson
Page 68 and 69:
Carbonate-hosted Zn-Pb-Ag mineralis
Page 70 and 71:
Fig. 3. New Zn-Pb-Ag occurrence, ea
Page 72 and 73:
Analyses of three mineralised vein
Page 74 and 75:
Karrat 97: reconnaissance mineral e
Page 76 and 77:
56° 54° 52° 0 50 km 56° 54° 52
Page 78 and 79:
Mineral occurrences and exploration
Page 80 and 81:
mainly defined by heavy mineral con
Page 82 and 83:
Hydrothermal activity in the Upper
Page 84 and 85:
A B 10 µm 10 µm C D 10 µm 10 µm
Page 86 and 87:
A B Gn Cp Cp Py Sp 50 µm 100 µm G
Page 88 and 89:
Christiansen, F.G., Piasecki, S., S
Page 90 and 91:
Fig. 2. Common Pb diagram with mant
Page 92 and 93:
Fig. 3. Sm-Nd isochron plot for dat
Page 94 and 95:
Mojzsis, S.J., Arrhenius, G., McKee
Page 96 and 97:
supracrustal succession is thus at
Page 98 and 99:
olite’, a unit that was traced al
Page 100 and 101:
sequence. In: Sidorenko, A.V. (ed.)
Page 102 and 103:
Fig. 1. Lithotectonic sketch map of
Page 104 and 105:
Fig. 3. Archaean basement gneisses
Page 106 and 107:
Fig. 5. Tectonic contact between Ar
Page 108 and 109:
Fig. 6. Two sets of mafic dykes fro
Page 110 and 111:
2. Emplacement ages and exhumation
Page 112 and 113:
Reassessment of the north-western b
Page 114 and 115:
Fig. 2. The basal part of the Ketil
Page 116 and 117:
▲ ▲ ▲ ▲ NNW shortening Tran
Page 118 and 119:
the dating of individual granite pl
Page 120 and 121:
North-East Greenland 1997-1998: a n
Page 122 and 123:
Fig. 2. Stauning Alper with summits
Page 124 and 125:
Fig. 4. The oldest parts of the cry
Page 126 and 127:
Fig. 6. Exposures of part of the Ym
Page 128 and 129:
Henriksen, N. 1998: Geological fiel
Page 130 and 131:
20 53° 51° 54°15' 54° 53°45' 4
Page 132 and 133:
Fig. 3. Range chart of selected pal
Page 134 and 135:
Palynostratigraphy The dinoflagella
Page 136 and 137:
epresents an overall progradation o
Page 138 and 139:
(ed.): Petroleum geology of Northwe
Page 140 and 141:
53° 51° 72° Inland Ice 72° Gree
Page 142 and 143:
from the Carlsberg Foundation, and
Page 144 and 145:
55 m 454 m a.s.l. 453 Samples Hystr
Page 146 and 147:
Seismic investigations offshore Sou
Page 148 and 149:
0.0 DLC97 Line 11 Leg 163, Site 988
Page 150 and 151:
68˚N 44˚W 42˚W 40˚W 38˚W 36˚W
Page 152 and 153:
tirelessly operating the seismic ge
Page 154 and 155:
Fig. 2. Block with ultramafic xenol
Page 156 and 157:
Late Cenozoic wood from Washington
Page 158 and 159:
Table 1. Data on wood pieces from N
Page 160 and 161:
Pingos at Nioghalvfjerdsfjorden, ea
Page 162 and 163:
A B C D E F Fig. 3. Pingos in the o
Page 164 and 165:
Late Quaternary palaeo-oceanography
Page 166 and 167:
600m waterdepth 250m 250m 250m 250m
Page 168 and 169:
flow deposits with a considerable a
Page 170 and 171:
A B Fig. 2. A: Lake G97-19 (60°04.
Page 172 and 173:
Facing page Fig. 3. Limnological me
Page 174 and 175:
7 8 5 Geology 1:500 000 10 Quaterna
Page 176 and 177:
1997/124 Investigation of the ore p
show all

Review of Greenland activities 1997 - Geus

Create successful ePaper yourself

Delete template?

Save as template?